1. Field of the Invention
This invention relates to a recording and reproducing system wherein a reproduction signal outputted from a compact disc reproducing section is recorded by a digital signal recording and reproducing section.
2. Description of the Prior Art
Ordinary analog audio apparatus such as, for example, cassette tape players are low in fidelity in recording and reproduction of sound, and when a temperature variation occurs with them or vibrations are applied to them, an increase in wow and flutter or a variation in reproducing speed occurs with them, which deteriorates the quality of a reproduction signal of them more or less.
On the other hand, digital-signal recording and reproducing apparatus as represented by compact disc players and digital audio tape recorders are designed principally for an audio signal and record and reproduce an audio signal in the form of a digital signal, and are very high in fidelity. Further, an error of a signal arising from a record medium itself or an error occurring at reading means is corrected by mighty error correcting processing, and the quality of a reproduction signal is deteriorated seldom with such digital signal recording and reproducing apparatus. Besides, wow and flutter upon reading is absorbed completely by storing data, which include such wow and flutter, once into a memory and then reading out them at a fixed rate.
Since a digital audio apparatus does not exhibit an influence thereupon of severe environment within a particular range, the superior characteristics described above are exhibited also when a reproduction signal of a digital audio signal reproducing unit is recorded by means of a digital audio signal recording unit in an automobile. In the following, description will be given of recording of a reproduction signal of a compact disc player (hereinafter referred to as CD section) by means of a digital audio signal recording and reproducing apparatus such as, for example, a digital audio tape recorder (hereinafter referred to as DAT section) in a room of a vehicle.
Referring to FIG. 17, there is shown an audio system which includes a car-carried CD section 100 and a car-carried DAT section 101 combined to each other such that an audio signal output 103 of the CD section 100 is connected to a recording signal input 104 of the DAT section 101. The CD section 100 includes a plurality of operating input keys including a CD-PLAY key 105 for instructing starting of reproduction or cancellation of a pause mode, a CD-PAUSE key 106 for instructing temporary interruption of reproduction, a CD-SEARCH key 107 for instructing heading of a track, and a CD-STOP key 108 for instructing stopping of reproduction. The CD section 100 has an operation panel having a disc insertion opening 109 formed therein and having a CD displaying section 110 provided thereon for displaying a time and so forth thereon.
Meanwhile, the DAT section 101 includes a plurality of operating keys including a DAT-PLAY key 111 for instructing starting of reproduction or cancellation of a recording waiting condition to start recording, a REC-PAUSE key 112 for instructing a recording waiting condition, a DAT-STOP key 113 for instructing stopping of recording or reproduction, and a DAT-SEARCH key 114 for instructing heading of a track. The DAT section 101 has an operation panel having a cassette pack insertion opening 115 therein and having a DAT displaying section 116 provided thereon for displaying a time and so forth thereon.
A recording operation is performed in the following procedure by manual operations of an operator. First, a compact disc not shown will be loaded in position into the CD section 100, and the CD-PLAY key 105 will be manually operated to instruct the CD section 100 starting of reproduction. Then, the CD-PAUSE key 106 will be manually operated, and a track the operator wants to start to record is inputted using the CD-SEARCH key 107. Consequently, the reproducing position of the CD section 100 is moved to a position near the head of the track, and then the recording and reproducing system waits in a pause condition. Then, a magnetic tape not shown will be loaded in position into the DAT section 101, and then the REC-PAUSE key 112 will be manually operated. Consequently, the trace position of the DAT section 101 automatically leaves a starting end of the tape (a leader portion of the tape) and is fed to a magnetic portion of the tape, thereby entering a recording waiting condition. Then, when the CD-PLAY key 105 of the CD section 100 and the DAT-PLAY key 111 of the DAT section 101 are manually operated substantially at the same time, the two apparatus 100 and 101 are released from the pause conditions, and the CD section 100 starts reproduction of the compact disc from the head of the track the operator wants to start to record while the DAT section 101 starts recording.
The conventional recording and reproducing system having the functions described above has such internal construction as shown in FIG. 18. Referring to FIG. 18, the CD section 100 includes a spindle motor 3 for applying turning force to a disc 2, an optical pickup 4 for reading a signal from the disc 2, and a servo circuit 5 having various servo functions necessary to read a signal and including an in-focus judging circuit 5a for judging, from an amount of returning light received from the disc 2 by the optical pickup 4, whether or not focusing servoing for the disc 2 is proceeding regularly.
The CD section 100 further includes a CD digital signal processing circuit 6 for processing a read signal. The CD digital signal processing circuit 6 includes a clock reproducing circuit 6a for reproducing bit clocks for data from a read signal, a CLV (constant linear velocity) servo circuit 6b for controlling rotation of the disc 2, a sub code demodulating circuit 6c, an EFM demodulating circuit 6d for demodulating an EFM modulated signal which is a modulating method peculiar to a compact disc, an error correcting circuit 6e, and a digital audio interface transmitting circuit 6f.
The CD section 100 further includes a CD memory 7 necessary for the temporary saving of data of the CD digital signal processing circuit 6 and the absorption of unevenness of a data reading speed, a CD operating circuit 8, a CD controlling circuit 9 for controlling operation of the entire CD section 100, and a CD voltage reduction detecting circuit 10 for checking a voltage reduction of a power supply input to the CD section 100 and for determining operation of the system from a result of the checking. The CD section 100 further includes an accessory power source 11 connected to an engine key of the vehicle, a battery power source 12 directly coupled to a battery not shown of the vehicle, a servo control line 13 for transmitting a controlling instruction to the servo circuit 5 and for monitoring an operating condition of the servo circuit 5, a CD sub code fetching line 14 for fetching sub code information therethrough, and a clock reproducing and synchronization detecting monitor line 15 for reproducing bit clocks from a read signal therethrough and further executing checking therethrough whether or not a detecting operation for a synchronizing signal is proceeding normally.
Meanwhile, the DAT section 101 includes a rotary drum and a motor 51, a pair of recording and reproducing heads 52 mounted on the rotary drum 51, a pinch roller 53, a capstan and a capstan motor 54, a DAT tape cassette 55, and a recording and reproduction amplifier circuit 56. The DAT 101 further includes a DAT digital signal processing circuit 57 which performs, upon recording, production of an error code, production of a sub code and 8-10 modulation peculiar to a DAT and performs, upon reproduction, correction of an error, demodulation of a sub code and 8-10 demodulation.
The DAT section 101 further includes a digital audio interface receiving circuit 58, an analog to digital converting circuit 59 for converting an analog signal of an analog recording source into a digital signal, a recording analog input terminal 60 for receiving an analog signal from an external analog recording source, a recording signal processing circuit 61 for selecting a digital audio interface input from the digital audio interface receiving circuit 58 or an analog input from the analog to digital converting circuit 59 and executing detection of a silence or no-sound condition, a DAT operating circuit 62, and a DAT voltage reduction detecting circuit 63 for checking a voltage reduction of a power supply input to the DAT section 101 and determining an operation of the system from a result of the checking.
The DAT section 101 further includes a DAT controlling circuit 64 for controlling operation of the entire DAT section 101, a drum capstan servo circuit 65 for controlling rotation of the rotary drum 51 and the capstan 54, a digital audio interface signal line 66, a detecting line 67 for a silence or no-sound signal detected by the recording signal processing circuit 61, a DAT sub code fetching line 68 for fetching a sub code read therethrough, and a recording sub code output line 69 for transmitting a sub code therethrough upon recording. In FIG. 14, the recording and reproducing system is shown in a condition so-called digital dubbing wherein a no-sound signal is being transmitted from the CD section 100 to the DAT section 101 by way of the digital audio interface signal line 66.
In the recording and reproducing system of the construction described above, the DAT section 101 performs, during a recording operation, recording of an audio signal and also records sub code information regarding the head or a number of a track or time. Sub code information required in the minimum for the DAT section 101 is information of the head of a track, and recording of such signal will be described below. When the CD section 100 or some other audio source is inputted to the DAT section 101, the DAT section 101 detects a change-over between tracks (track numbers) basically in accordance with either one of the following two methods.
The first one is used when a reproduction signal of the CD section 100 which is an object for recording is introduced into the DAT section 101 in a digital audio interface format specified by the Standards CP-340 of the Electronic Industrial Association of Japan (EIAJ). In case the recording source is the CD section 100, sub code information from which an interval between tracks can be detected is included in a digital signal from the CD section 100, and a change-over between tracks is detected making use of such sub code information.
The second method is used mainly when a signal of an object for recording is an analog signal or when, even if a signal of an object for recording is inputted in a digital audio interface format, either no inter track interval information is included in such signal or inter track interval information is included but is not utilized. When the DAT section 101 detects that a condition wherein the level of an audio signal is very low (i.e., silence or no-sound condition) has continued for more than a fixed period of time (for example, 2 seconds), it judges that an inter track interval is there.
The first method is performed by the digital audio interface receiving circuit 58, and a change-over between tracks thus detected by the digital audio interface receiving circuit 58 is transmitted to the DAT controlling circuit 64 by way of the no-sound detecting line 67. On the other hand, the principle of the second method of detecting a no-sound condition will be described subsequently. When a recording signal inputted to the DAT section 101 is an analog signal, the DAT section 101 PCM (pulse code modulation) converts the input recording signal finally into data of a two's complement format of 16 bits by means of the A/D converting circuit 59. In this instance, the relationship between the audio level and a digital code is such as illustrated in FIG. 19.
Now, if the columns are reversed only when the MSB of 16-bit data is equal to 1, then the relationship illustrated in FIG. 20 is obtained. The relationship thus obtained is equivalent to a result of full-wave rectifying processing of the 16-bit data. A level of an audio signal can be performed by comparing the value thus obtained with a digital value corresponding to a signal level as a threshold value for judgment of a no-sound condition by means of a digital comparator to judge a relationship in magnitude between them. For example, if the threshold signal level for no-sound judgment is about -60 dB of the full scale, then the binary value of "11111" makes the threshold value, and after all, if "1" is included in the high-order 11 columns of the data after the reversal described above, then this signifies presence of sound.
Determination of a no-sound condition is performed when the time wherein a no-sound condition is determined in the level judgment described above has continued for more than a fixed period of time. The recording signal processing circuit 61 has the function of such no-sound judgment and transmits a result of detection to the DAT controlling circuit 64 by way of the no-sound detecting line 67. When the DAT controlling circuit 64 detects, during recording, an inter track interval in accordance with either of the methods, it produces a signal for the recording sub code output line 69 so that sub code information representing the head of a track called nine second start ID may be recorded in addition to a music signal of a next piece of musing starting from the head of the track. The DAT digital signal processing circuit 57 combines the sub code information with the main recording signal.
FIG. 21 illustrates a relationship between a track number and a start ID. Meanwhile, FIG. 22 illustrates contents of an entire sub code of the DAT section 101 in which a start ID is included in a region denoted at SW1. Reference character SYNC in FIG. 22 denotes a synchronizing signal of the sub code. Such sub code is recorded, on a DAT tape, into a sub-area of a data array on a track of a tape shown in FIG. 23. An audio signal after digitalization is recorded into a main area of the track, and a tracking servo signal is recorded into an ATF area of the track. A heading operation during DAT reproduction is performed such that, while the tape is being fed fast, a start ID is detected, and while monitoring such start ID, the tape is fed at an ordinary speed or at a speed near to such ordinary speed until the reproducing position is set to a position a little forwardly of a position where the start ID appears.
It is to be noted that description of a heading operation at the CD section 100 upon reproduction is omitted herein since various products having such function have been realized.
As described so far, it is possible even in a room of a vehicle that a reproduction signal of the CD section 100 is recorded by a digital audio signal recording apparatus represented by the DAT section 101, and the quality in recording is normally sufficiently high. However, the environment in the vehicle room may sometimes be put into a very severe condition. For example, the room temperature may drop to -25.degree. C. or rise to 70.degree. C., or very strong vibrations or a very strong shock may be applied. In any of those severe situations, the CD section 100 and the DAT section 101 do not always operate regularly.
As regards a temperature factor, since the operator itself is in the environment, it can predict a disabled condition of the CD section 100 or the DAT section 101 and can avoid such disabled condition or an abnormal condition during recording. However, as regards a problem of jumping of sound (displacement from a track) or a break of sound at the CD section 100 caused by vibrations or a shock, it is difficult to eliminate them completely due to the facts that they occur unexpectedly, that a condition of a road cannot be predicted readily and that, even if a road is bad, the course of travel cannot always be changed. Consequently, when recording is performed in the vehicle room by a combination of the CD section 100 and the DAT section 101 having conventional functions, an abnormal sound or an interrupted sound may be included in recorded sound due to sudden jumping of sound at the CD section 100.
Most of vehicle-carried CD players have a function that, should jumping of sound or a break of sound occur, it is detected rapidly and then the trace position is returned to a previous reproducing position or a position near such position to resume reproduction. However, the time required for such returning operation is not so short that an abnormal condition does not occur in recorded sound.
In the prior art recording and reproducing system shown in FIG. 17, when jumping of sound or a break of sound occurs, an operator itself will manually operate the CD-SEARCH key 107 and the CD-PAUSE key 106 to move the reproducing position of a CD to a head portion of a particular track and then wait there. At the DAT section 101, the DAT-STOP key 113 will be operated to cancel a recording mode once, and then the trace position will be returned to the head of a particular track among already recorded tracks and wait there for recording by operation of the DAT-SEARCH key 114 and the REC-PAUSE key 112, whereafter reproduction of the CD section 100 and recording of the DAT section 101 will be resumed by operation of the CD-PLAY key 105 and the DAT-PLAY KEY 111. The particular track in this instance may normally be a track which is currently reproduced and recorded.
While the operations described above presume at all that the operator can detect jumping of sound, if a strong shock is applied to the vehicle, then since the noise is so high that members of the vehicles may not always listen to the music, jumping of sound or an instantaneous break of sound may possibly be missed.
Meanwhile, in case an analog signal is to be recorded, or even in case a digital audio interface is to be recorded but has no inter track information, when there is a no-sound interval of a suitable length between tracks, the inter track interval detecting means functions correctly upon recording at the DAT section 101 and also a start ID is recorded correctly. However, in a particular musical medium such as, for example, an on-the-spot recorded (live recorded) musical medium, while track numbers are originally different on sub codes of a compact disc, a reproduction signal is not be interrupted also at a change-over point between tracks.
Conventionally, in the case of such a disc as described just above, while it is being recorded or after recording of all tracks is completed once, an operator must necessarily perform a manual writing operation of start IDs, and such special operation is difficult in recording in a vehicle room.
With the conventional recording and reproducing system described above, while it is possible to record a reproduction signal of a CD by means of the digital signal recording apparatus in the vehicle room, if jumping of sound should occur once during recording, then an abnormal condition of a signal recorded by jumping of sound or a break of sound cannot be repaired unless the operator operates in a procedure including many steps. Further, it is a problem for safety of driving of the vehicle that many operations for repair of an abnormal condition are called for the driver. Such problems similarly apply to conventional recording and reproducing systems for domestic use.